From the standpoint of improving the output power, mileage, and exhaust gas performance or the reduction of size and weight of internal combustion engines, there is a very high demand for designs having cylinder liners in the cylinder bores of an aluminum cylinder block, and as a substitute technology, progress has been made in thermal spraying technology for forming a thermally sprayed film made of a ferrous material on the aluminum cylinder bore inner surface.
Japanese Publication Patent Application (Kokai) No. 2002-155350 discloses a technology in which, in order to increase the degree of adhesion of the thermally sprayed film, a rough surface is formed by pre-processing the cylinder bore inner surface to create embossed threads.